LPeg library for the Lua language version 5.1

LPeg is a new pattern-matching library for Lua, based on Parsing Expression
Grammars (PEGs). PEGs look similar to regular expressions or context-free
grammars in Backus-Naur form (BNF) notation. PEGs make a good replacement for
regular expressions, because they are strictly more powerful. For example, a
regular expression inherently cannot find matched pairs of parentheses, because
it is not recursive, but a PEG can.